#include <bits/stdc++.h>
using namespace std;
//#include<atcoder/all>
//using namespace atcoder;
#define rep(i,n) for (int i= 0; i < n; ++ i)
#define REP(i,n) for (int i= 1; i <= n; ++ i)
using ll = long long ;
using P = pair<int,int>;
//using mint = modint998244353;
using Graph=vector<vector<int>>;
const int INF=1001001001;
const int dx[4]={1,-1,0,0};
const int dy[4]={0,0,1,-1};
const long double EPS=1e-14;
const ll MOD=998244353;
int main() {
  ll a,b,t=1;
  cin>>a>>b;
  if(a<b) swap(a,b);
  while (1){
      if(t>a) break;
      t*=2;
  }
  cout<<min(t/2-1,b)<<endl;
}